When one misspells something not due to a typo or because they genuinely didn't know how to spell it, but when their mind subconsciously thinks of a common misspelling and one types it without thinking, due to their mind being more focused on other things, or for various other reasons.

Spelling genius "genious" when you in reality know how to spell it it correctly.

When you are casually texting someone and, either by your own mistake or by autocorrect, you turn the conversation sexy by an accidental typo. Tends to happen most often when you're talking to a crush/object of desire.